Re: Subject: Re: [Elecraft] RTTY filter for K3
Nyquist in this context does not refer to the Nyquist criterion (i.e. that the sample rate must be more than twice the highest signal frequency). It just means a filter that has no inter-symbol interference at a certain symbol rate (baud rate). It turns out that if you start with completely unfiltered symbols (a series of infinitely-narrow impulses, one per symbol) a Nyquist filter has the property that the frequency response is anti-symmetrical around 1/2 the symbol rate. One example of a Nyquist filter is a raised-cosine filter. The frequency response (plotted on a linear, not dB scale) is 1.0 from zero Hz up to (1-alpha) * symbol_rate/2 and is zero for all frequencies above (1+alpha) * symbol_rate/2. Between 1-alpha and 1+alpha, the frequency response has the shape of a raised cosine, smoothly going from 1.0 to 0.0. If you plot that on graph paper, you can see that the frequency response is anti-symmetrical about symbol_rate/2. (Alpha is a design parameter - the smaller the alpha the sharper the cutoff.) It is much easier to make a Nyquist filter digitally than with analog components, but you could approximate one with coils and capacitors. Actually, even the digital filter is an approximation since it theoretically has to have an impulse response that extends from -infinity to +infinity. That's probably more than you wanted to know. :=) Al N1AL On Mon, 2008-05-19 at 18:35, Art wrote: I must be confused by this filter discussion. Is not a Nyquist filter by its very definition a digital filter? Not directly comparable to the crystal filters in the K3 or any other rig. I would have supposed a Nyquist filter is one that samples at least twice per cycle at the highest observed frequency. As to what comes out of crystal filters, i.e. rtty tones, different discussion. If I have the processing chain figured correctly crystal filter output is then sampled by the audio card. I'm not a filter designer. Just asking based on previous experiences. 73 Art ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Alan Bloom wrote: It might be possible to use separate Nyquist filters and detectors for the two tones, treating each one as if it were a separate on/off-keyed signal. If the transmitted signal is not filtered too heavily (i.e. jumps quickly from one tone to the other) it seems like that should work. My impression was that that was the expected way of handling RTTY signals. Transmitter circuits from 1968 simply switched between two oscillators to key the signal; they didn't try to make a smooth transition in the frequency domain. -- David Woolley Emails are not formal business letters, whatever businesses may want. RFC1855 says there should be an address here, but, in a world of spam, that is no longer good advice, as archive address hiding may not work. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: Subject: Re: [Elecraft] RTTY filter for K3
Al Not at all, I'm sure you've helped more than just me! Thanks for the info. 73 Art Alan Bloom wrote: Nyquist in this context does not refer to the Nyquist criterion (i.e. that the sample rate must be more than twice the highest signal frequency). It just means a filter that has no inter-symbol interference at a certain symbol rate (baud rate). It turns out that if you start with completely unfiltered symbols (a series of infinitely-narrow impulses, one per symbol) a Nyquist filter has the property that the frequency response is anti-symmetrical around 1/2 the symbol rate. One example of a Nyquist filter is a raised-cosine filter. The frequency response (plotted on a linear, not dB scale) is 1.0 from zero Hz up to (1-alpha) * symbol_rate/2 and is zero for all frequencies above (1+alpha) * symbol_rate/2. Between 1-alpha and 1+alpha, the frequency response has the shape of a raised cosine, smoothly going from 1.0 to 0.0. If you plot that on graph paper, you can see that the frequency response is anti-symmetrical about symbol_rate/2. (Alpha is a design parameter - the smaller the alpha the sharper the cutoff.) It is much easier to make a Nyquist filter digitally than with analog components, but you could approximate one with coils and capacitors. Actually, even the digital filter is an approximation since it theoretically has to have an impulse response that extends from -infinity to +infinity. That's probably more than you wanted to know. :=) Al N1AL On Mon, 2008-05-19 at 18:35, Art wrote: I must be confused by this filter discussion. Is not a Nyquist filter by its very definition a digital filter? Not directly comparable to the crystal filters in the K3 or any other rig. I would have supposed a Nyquist filter is one that samples at least twice per cycle at the highest observed frequency. As to what comes out of crystal filters, i.e. rtty tones, different discussion. If I have the processing chain figured correctly crystal filter output is then sampled by the audio card. I'm not a filter designer. Just asking based on previous experiences. 73 Art ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Using a excessively narrow filter on RTTY is a balancing act. If the bandwidth is too narrow the tones tend to become smeared - the transitions become less easy to detect (in other words, the eye begins to close). However, narrowing the bandwidth also reduces the amount of QRM/QRN making it through the filter and to the decoder/detector. How about using a Nyquist filter? A Nyquist filter is one that results in no inter-symbol interference. One of the difficulties with RTTY is that the tone spacings are so wide. For a 45 baud FSK signal, a shift of about 30 Hz would minimize the occupied bandwidth and have no intersymbol interference. But standard practice is to use 170 Hz or 200 Hz shift. [ 200 Hz Shift is about right for 300 baud FSK, which is what we used (and why we used it) for HF packet some 25 years ago. And optimized it for common 400 Hz to 500 Hz wide CW crystal filters of that era. ] Thus, the rise of the dual tone filter (K3) and its work-alikes in various radios and demodulators, with fairly tight filters around each tone to pass it along with its significant sidebands. But the overall IF passband still needs to be wide enough to pass both tones and their sidebands. I imagine you can observe all of this on your P1. Some RTTY decoders take advantage of the tone separation and actually employ a pair of detectors, one for each tone, and use the outputs differentially to get some protection from selective fading. 170 Hz spacing is probably too close for such protection -- 850 Hz spacing would be better, but that requires an even wider IF passband... Some soundcard-based RTTY programs support really narrow shifts, but such signals are not often heard at this QTH. Maybe it is because everyone is listening and no one is calling CQ? Enjoy! Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Re: using Nyquist filters for RTTY. One complication I didn't mention is the fact that, because angle modulation (FM, FSK, PM, PSK) is fundamentally non-linear, the pre-detection and post-detection filters are fundamentally different. With linear modulation types (AM, on-off keying, QPSK, QAM), the spectrum of the pre-detection filter will appear the same at baseband. For example, if the IF filter has a 0.3-alpha Nyquist bandpass response, the resulting post-detection response at baseband will also be a 0.3-alpha Nyquist lowpass response. But that's not true with angle modulation. Using a Nyquist pre-detection filter does not result in a Nyquist response after detection. That is why most FSK and MSK systems use non-Nyquist filters (typically Gaussian). To use a Nyquist filter with FSK you would have to use a pre-detection filter much wider than the baud rate (as is done now for RTTY) and then add a Nyquist post-detection filter that would further tighten up the frequency response without causing additional inter-symbol interference. There may be a good reason why this is not usually done. When I get time maybe I'll do some Mathcad simulations to see if it looks like this could work. Some RTTY decoders take advantage of the tone separation and actually employ a pair of detectors, one for each tone, and use the outputs differentially to get some protection from selective fading. I think it is not just for selective fading but also for interference that occurs primarily on one of the two tones. It might be possible to use separate Nyquist filters and detectors for the two tones, treating each one as if it were a separate on/off-keyed signal. If the transmitted signal is not filtered too heavily (i.e. jumps quickly from one tone to the other) it seems like that should work. Al N1AL On Mon, 2008-05-19 at 07:00, Lyle Johnson wrote: Using a excessively narrow filter on RTTY is a balancing act. If the bandwidth is too narrow the tones tend to become smeared - the transitions become less easy to detect (in other words, the eye begins to close). However, narrowing the bandwidth also reduces the amount of QRM/QRN making it through the filter and to the decoder/detector. How about using a Nyquist filter? A Nyquist filter is one that results in no inter-symbol interference. One of the difficulties with RTTY is that the tone spacings are so wide. For a 45 baud FSK signal, a shift of about 30 Hz would minimize the occupied bandwidth and have no intersymbol interference. But standard practice is to use 170 Hz or 200 Hz shift. [ 200 Hz Shift is about right for 300 baud FSK, which is what we used (and why we used it) for HF packet some 25 years ago. And optimized it for common 400 Hz to 500 Hz wide CW crystal filters of that era. ] Thus, the rise of the dual tone filter (K3) and its work-alikes in various radios and demodulators, with fairly tight filters around each tone to pass it along with its significant sidebands. But the overall IF passband still needs to be wide enough to pass both tones and their sidebands. I imagine you can observe all of this on your P1. Some RTTY decoders take advantage of the tone separation and actually employ a pair of detectors, one for each tone, and use the outputs differentially to get some protection from selective fading. 170 Hz spacing is probably too close for such protection -- 850 Hz spacing would be better, but that requires an even wider IF passband... Some soundcard-based RTTY programs support really narrow shifts, but such signals are not often heard at this QTH. Maybe it is because everyone is listening and no one is calling CQ? Enjoy! Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Alan Bloom wrote: The problem is that different RTTY transmitters use different amounts of filtering. However I suspect that a Nyquist receive filter designed to compensate a typical/average transmit filter probably would have pretty good performance on most received signals. Does anyone know if this has ever been tried? With digital filters, one ought to be able to use the sort of adaptive filters used in modems, where the filter coefficients are adjusted by comparing the actual signal against the expected signal. Modems send a known training signal, to get fast initial convergence, but if the signal is at least marginally decodable, I would have though it would be possible get the filter to converge. One could probably start by making assumptions about the transmit filter and using known information about the receiver. This tactic will work better for synchronous systems, like PSK, but I would have thought it must be possible to train a filter off an asynchronous signal as well, although one might have solve for the signalling unit centre position after receiving the whole character. -- David Woolley The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio List Guidelines http://www.elecraft.com/elecraft_list_guidelines.htm ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Good point. It seems like an adaptive equalizer should work so long as propagation hasn't totally garbaged the signal. However, it would greatly increase the complexity of the demodulator. But maybe not if the equalizer assumes a simple model of the transmit filter and makes the a priori assumption that the channel does not change with time (i.e. ignores propagation). Al N1AL On Mon, 2008-05-19 at 14:59, David Woolley (E.L) wrote: Alan Bloom wrote: The problem is that different RTTY transmitters use different amounts of filtering. However I suspect that a Nyquist receive filter designed to compensate a typical/average transmit filter probably would have pretty good performance on most received signals. Does anyone know if this has ever been tried? With digital filters, one ought to be able to use the sort of adaptive filters used in modems, where the filter coefficients are adjusted by comparing the actual signal against the expected signal. Modems send a known training signal, to get fast initial convergence, but if the signal is at least marginally decodable, I would have though it would be possible get the filter to converge. One could probably start by making assumptions about the transmit filter and using known information about the receiver. This tactic will work better for synchronous systems, like PSK, but I would have thought it must be possible to train a filter off an asynchronous signal as well, although one might have solve for the signalling unit centre position after receiving the whole character. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Subject: Re: [Elecraft] RTTY filter for K3
I must be confused by this filter discussion. Is not a Nyquist filter by its very definition a digital filter? Not directly comparable to the crystal filters in the K3 or any other rig. I would have supposed a Nyquist filter is one that samples at least twice per cycle at the highest observed frequency. As to what comes out of crystal filters, i.e. rtty tones, different discussion. If I have the processing chain figured correctly crystal filter output is then sampled by the audio card. I'm not a filter designer. Just asking based on previous experiences. 73 Art ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
I think it is just the difference between books and the real world. I run AFSK, and with the K3 setup you can make full use of the filters. If I want to drill into a signal the 400hz works well. You leave a little drop off on each side. If you get it too narrow, the signal does not decode well. If you have issues beyond that, like I had when I hand two signals intermixing, then I went to the dual-pass-band filter, and that nails it down pretty hard. I have the 400hz, 1.0khz, newley received 1.8khz, and the 2.7khz, and it worked great in the volta rtty contest, and have used it some on 20m Friday evening. I am very happy with the setup. Start out with the 400hz, and put it in the second slot. If you want to add a 250 later, it takes about 15m to do it. Dave Wilburn K4DGW K2/100 - S/N 5982 K3/100 - S/N 766 For those who fought for it, freedom has a flavor the protected will never know. Axel Kaiser wrote: To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en-USform=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY filter for K3
The Elecraft 250 Hz 8-pole crystal filter is 370 Hz at the -6 dB point. You can run the DSP down as low as 300 Hz with this crystal filter and have minimal roll-off of the 170 Hz shift RTTY signal. In practice, I have run 200 Hz DSP in large RTTY pileups with great success in contests for months now. Yes, there is roll-off, but the narrower filter eliminated more of the pileup so that the net result was faster clear copy of at least one call sign, compared to even a 300 Hz DSP bandwidth. This trade-off was a net advantage. In non-pileup situations, the 300 Hz DSP bandwidth with the 250 Hz (actually 370 Hz) crystal filter is as narrow as you should, especially for weak signal reception. Furthermore the 400 and 500 Hz crystal filters are nearly as good as the 250 (really 370) for this application as roofing filters. In few cases, if any, will you be able to tell any difference between these three roofing filters. 73, Ed - W0YK -Original Message- From: [EMAIL PROTECTED] [mailto:elecraft- [EMAIL PROTECTED] On Behalf Of Axel Kaiser Sent: Sunday, May 18, 2008 5:15 AM To: Elecraft Reflector Subject: [Elecraft] RTTY filter for K3 To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en- USform=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
To try and answer this question completely, I generated a single Spectrogram plot showing: 1) A typical dual peak RTTY filter response (expect the K3 looks like this). It was from a Timewave DSP-559ZX. Receiver IF filter is about 350Hz. MTTY looks the same. 2) A RTTY signal. I haven't figured out how to post it here. Send me an E-mail and I'll send it to you. Bottom line: The DSP dual peak filter is 8-10 db down at a bandwidth of 260Hz. The actual signal fits completely within the minimally attenuated portion of the dual peak filter response. The concern about loosing information for weak signals is unfounded. The weak signal sidebands are so far in the noise that no information can be recovered. Theory about the sidebands being there is correct. It just doesn't consider this weak signal case. Thus the 250 Hz filter is plenty wide enough for SP and DXing. I'm not a believer in using AFC, even when running them during contests, but if you are, then perhaps a wider filter is more appropriate for that. 400Hz ought to be plenty wide enough. Guys who call you 100Hz or more off frequency don't deserve to be worked! I'll run this again when my K3 arrives. I don't expect the conclusions to change. More important is that the narrow filter response is centered within the passband. I note that available plots show 8 pole filters as much as 25 Hz from this. Five poles filters are probably even worse. Thus one needs to use the K3's ability to offset filters (of shift) for RTTY to achieve centering. Spectrogram is an easy to use, free tool to help sort things out. 73 de Brian/K3KO Axel Kaiser-2 wrote: To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en-USform=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- View this message in context: http://www.nabble.com/RTTY-filter-for-K3-tp17300221p17301567.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
The RTTY decoder in fldigi is very good - I use this source in DM780. Knowing how it works I am sure that a very tight 200Hz or 250Hz filter would be fine. In fact it would be interesting to compare the K3's RTTY decoding with external software, I'll do this sometime... Simon Brown, HB9DRV -- From: K3KO [EMAIL PROTECTED] Thus the 250 Hz filter is plenty wide enough for SP and DXing. I'm not a believer in using AFC, even when running them during contests, but if you are, then perhaps a wider filter is more appropriate for that. 400Hz ought to be plenty wide enough. Guys who call you 100Hz or more off frequency don't deserve to be worked! ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Axel I was the first to respond to your question. I told you that I was listening to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the experts came on here and using many words, explained why it couldn't work because it is too narrow. Maybe they do not actually have the filter but I do. Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal easily fits within the waterfall's passband with a little room on either side. The vertical stripes of the RTTY signal do not quiet reach the outer edge of the waterfall which tells me that the data is not being chopped off. Both weak and strong RTTY signals seem perfectly copyable. No I would not use this in a contest unless I had a bandscope so I could find signals. I have ordered the LP-PAN which should take care of that little detail. 73 Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 4:14 AM Subject: [Elecraft] RTTY filter for K3 To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en-USform=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Order a 400 cycle filter and be done with it. You won't miss a contact. Ken http://www.cashcowhunter.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Please turn on the K3 dual peak RTTY filter and tell us what you see then. Brian/K3KO n4lq wrote: Axel I was the first to respond to your question. I told you that I was listening to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the experts came on here and using many words, explained why it couldn't work because it is too narrow. Maybe they do not actually have the filter but I do. Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal easily fits within the waterfall's passband with a little room on either side. The vertical stripes of the RTTY signal do not quiet reach the outer edge of the waterfall which tells me that the data is not being chopped off. Both weak and strong RTTY signals seem perfectly copyable. No I would not use this in a contest unless I had a bandscope so I could find signals. I have ordered the LP-PAN which should take care of that little detail. 73 Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 4:14 AM Subject: [Elecraft] RTTY filter for K3 To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en-USform=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- View this message in context: http://www.nabble.com/RTTY-filter-for-K3-tp17300221p17303427.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
At 01:14 AM 18 05 2008, Axel Kaiser, DL3ZH wrote: This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . Lieber Axel, I use the 250 Hz all the time with my Omni VI+. Great performance: good copy and little interference. Perhaps PBT needs tweaking. I use the waterfall display and adjust PBT to center passband on the two RTTY tones. 73, Hank, W6SX Mammoth Lakes, California Elevation 8083 feet in John Muir's Range of Light ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
I'm using DATA A mode. Contrary to the manual, the Dual Tone RTTY filter will not activate in DATA A mode. When attempted, the display shows N/A. To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. As far as copying RTTY with the 200hz filter and DTFIt appears to work fine. The only difference I could detect on the waterfall with DTF turned on is the obvious hole between the filter peaks. Steve Ellington [EMAIL PROTECTED] - Original Message - From: K3KO [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 10:12 AM Subject: Re: [Elecraft] RTTY filter for K3 Please turn on the K3 dual peak RTTY filter and tell us what you see then. Brian/K3KO n4lq wrote: Axel I was the first to respond to your question. I told you that I was listening to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the experts came on here and using many words, explained why it couldn't work because it is too narrow. Maybe they do not actually have the filter but I do. Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal easily fits within the waterfall's passband with a little room on either side. The vertical stripes of the RTTY signal do not quiet reach the outer edge of the waterfall which tells me that the data is not being chopped off. Both weak and strong RTTY signals seem perfectly copyable. No I would not use this in a contest unless I had a bandscope so I could find signals. I have ordered the LP-PAN which should take care of that little detail. 73 Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 4:14 AM Subject: [Elecraft] RTTY filter for K3 To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en-USform=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- View this message in context: http://www.nabble.com/RTTY-filter-for-K3-tp17300221p17303427.html Sent from the Elecraft mailing list archive at Nabble.com. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM
Re: [Elecraft] RTTY filter for K3
You can change the MARK freq in AFSK A mode to one of four values ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU n4lq wrote: To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Yes but it won't change the center fq. to 1500Hz so it will be like DATA A. I'm not sure what the purpose of changing the pitch is. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 2:43 PM Subject: Re: [Elecraft] RTTY filter for K3 You can change the MARK freq in AFSK A mode to one of four values ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU n4lq wrote: To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
As far as I know, the reason for having the capability of changing the Mark freq is for personal preference in what you like to listen to. The Dual PB filter works at whatever frequency you select. I can think of no reason why AFSK A and DATA A modes would necessarily have to be the same. I'm not sure why you want to change the center frequency to specifically 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. I prefer the lower mark frequency of 915 Hz. The software that is decoding the signal sure doesn't care and it doesn't make any difference to what you are sending. But as they say here ofter YMMV. 73, Ken K3IU ~ n4lq wrote: Yes but it won't change the center fq. to 1500Hz so it will be like DATA A. I'm not sure what the purpose of changing the pitch is. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 2:43 PM Subject: Re: [Elecraft] RTTY filter for K3 You can change the MARK freq in AFSK A mode to one of four values ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU n4lq wrote: To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Bear with me on this KenIt's long but hopefully I can explain.: By the same tokenI can see no reason why the center frequency of DATA A and AFSK A should be different. Most advanced digital mode programs such as MixW have something similar to an Align macro. You tell the macro what you filter's center frequency is then whenever you click on that macro it instantly tunes your K3 so that the desired trace on your waterfall is exactly centered in the IF passband. You can then choose your most narrow filter and that signal will still be in the IF's center. I have a macro for the filter selection too so everything is really fast and easy. Here's how it works for me. 1. K3 filter set on very wide3+ KHZ. 2. See signal on waterfall. 3. Click on signal. 4. Begin to copy data on screen. 5. Signal is weak, QRM, need narrow filter. 6. Click on Align macro. Signal is now centered in passband. 7. Click on filter macro, choosing 200Hz filter. 8. QRM gone...Signal now easy to copy. Now this was all in DATA A mode. I use DATA A for PSK31, MFSK and anyother digital mode. So what if I want to operate RTTY? Well I can go ahead and do so in DATA A mode however that DUAL FIL feature will not activate. Is this a flaw? So I got to AFSK ANow DUAL FIL works but now my ALIGN macro won't work because my IF Center is different. It should not be1500 HZ should be the default. If I wanted to use 910 HZ and enjoy that low pitch sound, I would have to either change my Align macro or try to manually tune the RTTY signal which is terribly difficult, especially in a contest when transmissions last for only a few seconds. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 3:37 PM Subject: Re: [Elecraft] RTTY filter for K3 As far as I know, the reason for having the capability of changing the Mark freq is for personal preference in what you like to listen to. The Dual PB filter works at whatever frequency you select. I can think of no reason why AFSK A and DATA A modes would necessarily have to be the same. I'm not sure why you want to change the center frequency to specifically 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. I prefer the lower mark frequency of 915 Hz. The software that is decoding the signal sure doesn't care and it doesn't make any difference to what you are sending. But as they say here ofter YMMV. 73, Ken K3IU ~ n4lq wrote: Yes but it won't change the center fq. to 1500Hz so it will be like DATA A. I'm not sure what the purpose of changing the pitch is. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 2:43 PM Subject: Re: [Elecraft] RTTY filter for K3 You can change the MARK freq in AFSK A mode to one of four values ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU n4lq wrote: To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Yes but it won't change the center fq. to 1500Hz so it will be like DATA A. I'm not sure what the purpose of changing the pitch is. DATA A is a general purpose mode. It is SSB with some features that could cause distortion (like the speech processor) disabled. It is data mode agnostic: you can run RTTY, PSK, Olivia, DRM, ... We also put some specialized modes under the DATA umbrella. AFSK, FSK D and PSK D are the current ones. AFSK and FSK D assume you are probably running RTTY, or at least an FSK mode with similar data rate and the same shift. The dual tone filter (DTF) is thus available for AFSK and for FSK D, but not for DATA A or PSK D. The reason for the various tone pairs is that some of you will likely want to run an external decoder and/or encoder (MTTY, or HRD+DM780, for example) and these programs often assume certain standard tone pairs will be used. We put the most popular of these as selectable pairs. 73, Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
OK... thanks Steve. I am familiar with MixW... have used it for years and I see what you are talking about. But let me suggest the following... Go to AFSK A mode and set the mark frequency to 1445. That will give you a center frequency of 1530 which would put you within 30 Hz of your align frequency of 1500 Hz. If signal is still a l'il off, then use mouse to get it on or let the AFC move it on. I just tried it on a PSK signal with my filter cranked down as narrow as it would go in Data Mode and it hardly missed a beat decoding. 73, Ken K3IU n4lq wrote: Bear with me on this KenIt's long but hopefully I can explain.: By the same tokenI can see no reason why the center frequency of DATA A and AFSK A should be different. Most advanced digital mode programs such as MixW have something similar to an Align macro. You tell the macro what you filter's center frequency is then whenever you click on that macro it instantly tunes your K3 so that the desired trace on your waterfall is exactly centered in the IF passband. You can then choose your most narrow filter and that signal will still be in the IF's center. I have a macro for the filter selection too so everything is really fast and easy. Here's how it works for me. 1. K3 filter set on very wide3+ KHZ. 2. See signal on waterfall. 3. Click on signal. 4. Begin to copy data on screen. 5. Signal is weak, QRM, need narrow filter. 6. Click on Align macro. Signal is now centered in passband. 7. Click on filter macro, choosing 200Hz filter. 8. QRM gone...Signal now easy to copy. Now this was all in DATA A mode. I use DATA A for PSK31, MFSK and anyother digital mode. So what if I want to operate RTTY? Well I can go ahead and do so in DATA A mode however that DUAL FIL feature will not activate. Is this a flaw? So I got to AFSK ANow DUAL FIL works but now my ALIGN macro won't work because my IF Center is different. It should not be1500 HZ should be the default. If I wanted to use 910 HZ and enjoy that low pitch sound, I would have to either change my Align macro or try to manually tune the RTTY signal which is terribly difficult, especially in a contest when transmissions last for only a few seconds. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 3:37 PM Subject: Re: [Elecraft] RTTY filter for K3 As far as I know, the reason for having the capability of changing the Mark freq is for personal preference in what you like to listen to. The Dual PB filter works at whatever frequency you select. I can think of no reason why AFSK A and DATA A modes would necessarily have to be the same. I'm not sure why you want to change the center frequency to specifically 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. I prefer the lower mark frequency of 915 Hz. The software that is decoding the signal sure doesn't care and it doesn't make any difference to what you are sending. But as they say here ofter YMMV. 73, Ken K3IU ~ n4lq wrote: Yes but it won't change the center fq. to 1500Hz so it will be like DATA A. I'm not sure what the purpose of changing the pitch is. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 2:43 PM Subject: Re: [Elecraft] RTTY filter for K3 You can change the MARK freq in AFSK A mode to one of four values ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU n4lq wrote: To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY filter for K3
Ok Ken but that's with a BW of 150Hz, not too critical. Soon, I am told, Elecraft will activate the 50Hz filter so it can be used in Data mode. I suggested to Lyle that they change the default center fq. in AFSK to 1500 so it will match Data A then let the user change as desired. Then also allow use of the Dual PB feature in Data A. That should perfect things. Then I would not even bother using AFSK A. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: Elecraft Reflector elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 5:04 PM Subject: Re: [Elecraft] RTTY filter for K3 OK... thanks Steve. I am familiar with MixW... have used it for years and I see what you are talking about. But let me suggest the following... Go to AFSK A mode and set the mark frequency to 1445. That will give you a center frequency of 1530 which would put you within 30 Hz of your align frequency of 1500 Hz. If signal is still a l'il off, then use mouse to get it on or let the AFC move it on. I just tried it on a PSK signal with my filter cranked down as narrow as it would go in Data Mode and it hardly missed a beat decoding. 73, Ken K3IU n4lq wrote: Bear with me on this KenIt's long but hopefully I can explain.: By the same tokenI can see no reason why the center frequency of DATA A and AFSK A should be different. Most advanced digital mode programs such as MixW have something similar to an Align macro. You tell the macro what you filter's center frequency is then whenever you click on that macro it instantly tunes your K3 so that the desired trace on your waterfall is exactly centered in the IF passband. You can then choose your most narrow filter and that signal will still be in the IF's center. I have a macro for the filter selection too so everything is really fast and easy. Here's how it works for me. 1. K3 filter set on very wide3+ KHZ. 2. See signal on waterfall. 3. Click on signal. 4. Begin to copy data on screen. 5. Signal is weak, QRM, need narrow filter. 6. Click on Align macro. Signal is now centered in passband. 7. Click on filter macro, choosing 200Hz filter. 8. QRM gone...Signal now easy to copy. Now this was all in DATA A mode. I use DATA A for PSK31, MFSK and anyother digital mode. So what if I want to operate RTTY? Well I can go ahead and do so in DATA A mode however that DUAL FIL feature will not activate. Is this a flaw? So I got to AFSK ANow DUAL FIL works but now my ALIGN macro won't work because my IF Center is different. It should not be1500 HZ should be the default. If I wanted to use 910 HZ and enjoy that low pitch sound, I would have to either change my Align macro or try to manually tune the RTTY signal which is terribly difficult, especially in a contest when transmissions last for only a few seconds. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 3:37 PM Subject: Re: [Elecraft] RTTY filter for K3 As far as I know, the reason for having the capability of changing the Mark freq is for personal preference in what you like to listen to. The Dual PB filter works at whatever frequency you select. I can think of no reason why AFSK A and DATA A modes would necessarily have to be the same. I'm not sure why you want to change the center frequency to specifically 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. I prefer the lower mark frequency of 915 Hz. The software that is decoding the signal sure doesn't care and it doesn't make any difference to what you are sending. But as they say here ofter YMMV. 73, Ken K3IU ~ n4lq wrote: Yes but it won't change the center fq. to 1500Hz so it will be like DATA A. I'm not sure what the purpose of changing the pitch is. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Ken K3IU [EMAIL PROTECTED] To: n4lq [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 2:43 PM Subject: Re: [Elecraft] RTTY filter for K3 You can change the MARK freq in AFSK A mode to one of four values ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU n4lq wrote: To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus
Re: [Elecraft] RTTY filter for K3
...I suggested to Lyle that they change the default center fq. in AFSK to 1500 so it will match Data A then let the user change as desired. The center frequency in AFSK will be between the two tones selected for the tone pair. It really can;t be anything else. DATA A is a general purpose data mode. AFSK is targeted for RTTY operation. 73, Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY filter for K3
I was the first to respond to your question. I told you that I was listening to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the experts came on here and using many words, explained why it couldn't work because it is too narrow. Using a excessively narrow filter on RTTY is a balancing act. If the bandwidth is too narrow the tones tend to become smeared - the transitions become less easy to detect (in other words, the eye begins to close). However, narrowing the bandwidth also reduces the amount of QRM/QRN making it through the filter and to the decoder/detector. In some cases the benefits of reduced interference are greater than the losses caused by data smearing in the too narrow filter. This is particularly true if the desired signal is strong enough in the absence of QRM/QRN to be decoded even with compromised bandwidth. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of n4lq Sent: Sunday, May 18, 2008 8:42 AM To: Axel Kaiser; Elecraft Reflector Subject: Re: [Elecraft] RTTY filter for K3 Axel I was the first to respond to your question. I told you that I was listening to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the experts came on here and using many words, explained why it couldn't work because it is too narrow. Maybe they do not actually have the filter but I do. Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal easily fits within the waterfall's passband with a little room on either side. The vertical stripes of the RTTY signal do not quiet reach the outer edge of the waterfall which tells me that the data is not being chopped off. Both weak and strong RTTY signals seem perfectly copyable. No I would not use this in a contest unless I had a bandscope so I could find signals. I have ordered the LP-PAN which should take care of that little detail. 73 Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Sunday, May 18, 2008 4:14 AM Subject: [Elecraft] RTTY filter for K3 To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vistamkt=en-USf orm=QBRE___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman
RE: [Elecraft] RTTY filter for K3
On Sun, 2008-05-18 at 19:27, Joe Subich, W4TV wrote: ... Using a excessively narrow filter on RTTY is a balancing act. If the bandwidth is too narrow the tones tend to become smeared - the transitions become less easy to detect (in other words, the eye begins to close). However, narrowing the bandwidth also reduces the amount of QRM/QRN making it through the filter and to the decoder/detector. How about using a Nyquist filter? A Nyquist filter is one that results in no inter-symbol interference. That is, the filtered output is guaranteed to pass exactly through the nominal symbol location at the middle of each symbol, no matter what data may have been sent in adjacent symbols. So you get the narrowest possible bandwidth without smearing the signal, closing the eye or whatever you want to call it. For that to work, the total response must be Nyquist, including both the filter in the transmitter as well as in the receiver. Many commercial systems use Root Nyquist filters in both the transmitter and receiver. Since each filter's frequency response is the square root of a Nyquist filter response, the total system response is Nyquist, resulting in no inter-symbol interference. However, most RTTY transmitters do not have such a filter. Typically they just use a single-pole R-C low-pass filter to limit the transmitted bandwidth. However, if the time constant of the R-C filter were known, it would be straightforward to design a receive filter that results in a net Nyquist response. The problem is that different RTTY transmitters use different amounts of filtering. However I suspect that a Nyquist receive filter designed to compensate a typical/average transmit filter probably would have pretty good performance on most received signals. Does anyone know if this has ever been tried? Al N1AL ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY Filter for K3
J. Edward (Ed) Muns wrote: I agree with Joe's summary. Note that the 250 Hz 8-pole filter is really about 370 Hz at the -6 dB point. Any of the current 500, 400 or 250 Hz crystal filters will be fine for RTTY. With any of them, the DSP can be narrowed to 300 Hz without rolling off the outside edges of the two tones. Note that the Dual-Tone Filter for RTTY is cascaded with the crystal and normal DSP filters and if either of the latter two filters are 250 Hz (at -6 dB) the three-filter-cascade will have significant roll-off on the outside skirts. This has the undesired effect of moving the two filter peaks much closer together than the 170 Hz split. That said, I have been running the 370 Hz crystal filter (aka 250 Hz 8-pole) with 200 Hz DSP and the DTF for several months now in RTTY contests. While the resultant passband was indeed rolled off as described, this was overall a net benefit in heavy pileup conditions because it filtered out the pileup better, producing a clear callsign quicker, despite the rolled-off passband. In other than heavy pileup conditions, it is best to keep the DSP at 300 Hz or higher, especially for copy of weaker signals. In the future, there will probably be a 200-400 (or 200-500) Hz variable 5-pole crystal filter that will be ideal to track with the DSP for high performance RTTY reception, ranging from weak signal to heavy pileup conditions. Thanks to both Joe and Ed. I hadn't realised just how wide Inrad's so-called 250Hz filter is. 50% wider than nominal is frankly ridiculous. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY Filter for K3
Hi Axel, full ack with Joe. I use the 400 Hz 8 Pole with a DSP of about 300-350 in dual tone. Perfect! 73! Frank, DD7ZT Joe Subich, W4TV schrieb: After making extensive tests and plotting the selectivity curves of the 200 Hz filter in my K3, I'm convinced that it is too narrow for reliable weak signal RTTY operation, particularly in conjunction with the dual-tone filter. The measured -6dB bandwidth of the 200 Hz crystal filter was 209 Hz and the composite bandwidth of the 200 Hz crystal filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 Hz filters with center frequencies separated by 170 Hz). After extended discussion with a well know RTTY op and K3 beta tester, I believe the combination of a 300 Hz 5-pole crystal filter, 300 Hz DSP and the dual tone filter will have a composite -6 dB bandwidth of about 250 Hz - about optimum for narrow RTTY. The currently available, 250, 400 or 500 Hz filters in combination with a 300 Hz DPS bandwidth and dual tone filter are very close to optimum. 73, ... Joe, W4TV Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY Filter for K3
Frank Lammel wrote: Joe Subich, W4TV schrieb: After making extensive tests and plotting the selectivity curves of the 200 Hz filter in my K3, I'm convinced that it is too narrow for reliable weak signal RTTY operation, particularly in conjunction with dual-tone filter.The measured -6dB bandwidth of the 200 Hz crystal filter was 209 Hz and the composite bandwidth of the 200 Hz crystal filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 Hz filters with center frequencies separated by 170 Hz). After extended discussion with a well know RTTY op and K3 beta tester, I believe the combination of a 300 Hz 5-pole crystal filter, 300 Hz DSP and the dual tone filter will have a composite -6 dB bandwidth of about 250 Hz - about optimum for narrow RTTY. The currently available, 250, 400 or 500 Hz filters in combination with a 300 Hz DPS bandwidth and dual tone filter are very close to optimum.73, ... Joe, W4TV Hi Axel, full ack with Joe. I use the 400 Hz 8 Pole with a DSP of about 300-350 in dual tone. Perfect! Many thanks to Joe for that analysis. However, that analysis applies only to weak signals in the absence of QRM. In the intense QRM conditions of RTTY contesting in Europe, I routinely use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. (Unfortunately the new Inrad website doesn't include filter plots, so it isn't possible to estimate the cumulative bandwidths of these cascaded filters.) When the channel is clear, copy of weak signals is not noticeably degraded compared with cascaded 500Hz filters; but when QRM appears, the narrower filters often make a decisive difference by preventing a strong unwanted tone from capturing the AGC. A 200Hz 5-pole filter for the K3 is arriving next week, and then I'll be able to do some A/B/C testing against the K3's own 400Hz filter and the 250+250 filters in the MP. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY Filter for K3
Ian, In the intense QRM conditions of RTTY contesting in Europe, I routinely use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. (Unfortunately the new Inrad website doesn't include filter plots, so it isn't possible to estimate the cumulative bandwidths of these cascaded filters.) The nasty little secret is that all of the INRAD 250 Hz filters in the 8 - 9 MHz range have -6 dB bandwidths around 325-375 Hz. That makes the original analysis accurate since your FT-1000MP is really using cascaded 370/300 Hz filters. The old Inrad site is still available at www.qth.com/inrad see the Yaesu 250 filters at: www.qth.com/inrad/graphs/704.gif (455 KHz) www.qth.com/inrad/graphs/708.gif (8125 KHz) 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ian White GM3SEK Sent: Friday, May 16, 2008 4:30 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] RTTY Filter for K3 Frank Lammel wrote: Joe Subich, W4TV schrieb: After making extensive tests and plotting the selectivity curves of the 200 Hz filter in my K3, I'm convinced that it is too narrow for reliable weak signal RTTY operation, particularly in conjunction with dual-tone filter.The measured -6dB bandwidth of the 200 Hz crystal filter was 209 Hz and the composite bandwidth of the 200 Hz crystal filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 Hz filters with center frequencies separated by 170 Hz). After extended discussion with a well know RTTY op and K3 beta tester, I believe the combination of a 300 Hz 5-pole crystal filter, 300 Hz DSP and the dual tone filter will have a composite -6 dB bandwidth of about 250 Hz - about optimum for narrow RTTY. The currently available, 250, 400 or 500 Hz filters in combination with a 300 Hz DPS bandwidth and dual tone filter are very close to optimum.73, ... Joe, W4TV Hi Axel, full ack with Joe. I use the 400 Hz 8 Pole with a DSP of about 300-350 in dual tone. Perfect! Many thanks to Joe for that analysis. However, that analysis applies only to weak signals in the absence of QRM. In the intense QRM conditions of RTTY contesting in Europe, I routinely use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. (Unfortunately the new Inrad website doesn't include filter plots, so it isn't possible to estimate the cumulative bandwidths of these cascaded filters.) When the channel is clear, copy of weak signals is not noticeably degraded compared with cascaded 500Hz filters; but when QRM appears, the narrower filters often make a decisive difference by preventing a strong unwanted tone from capturing the AGC. A 200Hz 5-pole filter for the K3 is arriving next week, and then I'll be able to do some A/B/C testing against the K3's own 400Hz filter and the 250+250 filters in the MP. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY Filter for K3
One thing I don't see mentioned much - something that makes ALL the difference in the world - is exactly *where* the bandwidth is measured on the response curve. Years ago I saw a lot of bandwidth measured at the -10 dB points (that was probably before many K3 owners were born - I haven't seen it for a long time but it was pretty common at one time). Then a *lot* of bandwidths were specified at the -3 dB or half power points. Now -6 dB seems popular. It seems like Inrad may be using -3 dB for some of their measurements. The corner of the bandpass is covered by the data, but it looks very much like that 455 kHz 300 Hz filter is 300 Hz wide at the -3 dB points. Ron AC7AC -Original Message- Ian, In the intense QRM conditions of RTTY contesting in Europe, I routinely use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. (Unfortunately the new Inrad website doesn't include filter plots, so it isn't possible to estimate the cumulative bandwidths of these cascaded filters.) The nasty little secret is that all of the INRAD 250 Hz filters in the 8 - 9 MHz range have -6 dB bandwidths around 325-375 Hz. That makes the original analysis accurate since your FT-1000MP is really using cascaded 370/300 Hz filters. The old Inrad site is still available at www.qth.com/inrad see the Yaesu 250 filters at: www.qth.com/inrad/graphs/704.gif (455 KHz) www.qth.com/inrad/graphs/708.gif (8125 KHz) 73, ... Joe, W4TV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY Filter for K3
It seems like Inrad may be using -3 dB for some of their measurements. The corner of the bandpass is covered by the data, but it looks very much like that 455 kHz 300 Hz filter is 300 Hz wide at the -3 dB points. Collins specified their mechanical filters at -3 dB. However, crystal filters in amateur literature have been specified at -6 dB for at least 30 years. Shape factor has been the ratio of -6 to -60 dB bandwidth for at least as long. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ron D'Eau Claire Sent: Friday, May 16, 2008 7:40 PM To: elecraft@mailman.qth.net Subject: RE: [Elecraft] RTTY Filter for K3 One thing I don't see mentioned much - something that makes ALL the difference in the world - is exactly *where* the bandwidth is measured on the response curve. Years ago I saw a lot of bandwidth measured at the -10 dB points (that was probably before many K3 owners were born - I haven't seen it for a long time but it was pretty common at one time). Then a *lot* of bandwidths were specified at the -3 dB or half power points. Now -6 dB seems popular. It seems like Inrad may be using -3 dB for some of their measurements. The corner of the bandpass is covered by the data, but it looks very much like that 455 kHz 300 Hz filter is 300 Hz wide at the -3 dB points. Ron AC7AC -Original Message- Ian, In the intense QRM conditions of RTTY contesting in Europe, I routinely use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. (Unfortunately the new Inrad website doesn't include filter plots, so it isn't possible to estimate the cumulative bandwidths of these cascaded filters.) The nasty little secret is that all of the INRAD 250 Hz filters in the 8 - 9 MHz range have -6 dB bandwidths around 325-375 Hz. That makes the original analysis accurate since your FT-1000MP is really using cascaded 370/300 Hz filters. The old Inrad site is still available at www.qth.com/inrad see the Yaesu 250 filters at: www.qth.com/inrad/graphs/704.gif (455 KHz) www.qth.com/inrad/graphs/708.gif (8125 KHz) 73, ... Joe, W4TV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY Filter for K3
I agree with Joe's summary. Note that the 250 Hz 8-pole filter is really about 370 Hz at the -6 dB point. Any of the current 500, 400 or 250 Hz crystal filters will be fine for RTTY. With any of them, the DSP can be narrowed to 300 Hz without rolling off the outside edges of the two tones. Note that the Dual-Tone Filter for RTTY is cascaded with the crystal and normal DSP filters and if either of the latter two filters are 250 Hz (at -6 dB) the three-filter-cascade will have significant roll-off on the outside skirts. This has the undesired effect of moving the two filter peaks much closer together than the 170 Hz split. That said, I have been running the 370 Hz crystal filter (aka 250 Hz 8-pole) with 200 Hz DSP and the DTF for several months now in RTTY contests. While the resultant passband was indeed rolled off as described, this was overall a net benefit in heavy pileup conditions because it filtered out the pileup better, producing a clear callsign quicker, despite the rolled-off passband. In other than heavy pileup conditions, it is best to keep the DSP at 300 Hz or higher, especially for copy of weaker signals. In the future, there will probably be a 200-400 (or 200-500) Hz variable 5-pole crystal filter that will be ideal to track with the DSP for high performance RTTY reception, ranging from weak signal to heavy pileup conditions. 73, Ed - W0YK -Original Message- From: [EMAIL PROTECTED] [mailto:elecraft- [EMAIL PROTECTED] On Behalf Of Joe Subich, W4TV Sent: Friday, May 16, 2008 12:28 AM To: 'n4lq'; elecraft@mailman.qth.net Subject: RE: [Elecraft] RTTY Filter for K3 I am watching RTTY right now and using the 200 Hz 5 pole filter. The 170 HZ shift fits perfectly within the passband. After making extensive tests and plotting the selectivity curves of the 200 Hz filter in my K3, I'm convinced that it is too narrow for reliable weak signal RTTY operation, particularly in conjunction with the dual-tone filter. The measured -6dB bandwidth of the 200 Hz crystal filter was 209 Hz and the composite bandwidth of the 200 Hz crystal filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 Hz filters with center frequencies separated by 170 Hz). After extended discussion with a well know RTTY op and K3 beta tester, I believe the combination of a 300 Hz 5-pole crystal filter, 300 Hz DSP and the dual tone filter will have a composite -6 dB bandwidth of about 250 Hz - about optimum for narrow RTTY. The currently available, 250, 400 or 500 Hz filters in combination with a 300 Hz DPS bandwidth and dual tone filter are very close to optimum. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of n4lq Sent: Thursday, May 15, 2008 5:29 PM To: Axel Kaiser; Elecraft Reflector Subject: Re: [Elecraft] RTTY Filter for K3 Axel: I am watching RTTY right now and using the 200 Hz 5 pole filter. The 170 HZ shift fits perfectly within the passband. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Thursday, May 15, 2008 3:52 PM Subject: [Elecraft] RTTY Filter for K3 Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale= en-ussource=wlmailtagline ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- -- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release Date: 5/15/2008 7:24 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release Date: 5/15/2008 7:24 AM ___ Elecraft mailing list
Re: [Elecraft] RTTY Filter for K3
Axel: I am watching RTTY right now and using the 200 Hz 5 pole filter. The 170 HZ shift fits perfectly within the passband. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Thursday, May 15, 2008 3:52 PM Subject: [Elecraft] RTTY Filter for K3 Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-ussource=wlmailtagline___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release Date: 5/15/2008 7:24 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RTTY Filter for K3
Hi Axel, DL3ZH, In my opinion, either one would be fine. I have the 400 Hz 8-pole in my K3, but, don't forget it is a roofing filter. In my RTTY setup, using the AFSK A digital mode, and I turn on the dual bandpass. The actual bandpass is then set by the DSP to two 50 Hz filters. It works great! 73, John, W2GW - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Thursday, May 15, 2008 3:52 PM Subject: [Elecraft] RTTY Filter for K3 Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-ussource=wlmailtagline___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RTTY Filter for K3
I am watching RTTY right now and using the 200 Hz 5 pole filter. The 170 HZ shift fits perfectly within the passband. After making extensive tests and plotting the selectivity curves of the 200 Hz filter in my K3, I'm convinced that it is too narrow for reliable weak signal RTTY operation, particularly in conjunction with the dual-tone filter. The measured -6dB bandwidth of the 200 Hz crystal filter was 209 Hz and the composite bandwidth of the 200 Hz crystal filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 Hz filters with center frequencies separated by 170 Hz). After extended discussion with a well know RTTY op and K3 beta tester, I believe the combination of a 300 Hz 5-pole crystal filter, 300 Hz DSP and the dual tone filter will have a composite -6 dB bandwidth of about 250 Hz - about optimum for narrow RTTY. The currently available, 250, 400 or 500 Hz filters in combination with a 300 Hz DPS bandwidth and dual tone filter are very close to optimum. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of n4lq Sent: Thursday, May 15, 2008 5:29 PM To: Axel Kaiser; Elecraft Reflector Subject: Re: [Elecraft] RTTY Filter for K3 Axel: I am watching RTTY right now and using the 200 Hz 5 pole filter. The 170 HZ shift fits perfectly within the passband. Steve Ellington [EMAIL PROTECTED] - Original Message - From: Axel Kaiser [EMAIL PROTECTED] To: Elecraft Reflector elecraft@mailman.qth.net Sent: Thursday, May 15, 2008 3:52 PM Subject: [Elecraft] RTTY Filter for K3 Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale= en-ussource=wlmailtagline ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- -- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release Date: 5/15/2008 7:24 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release Date: 5/15/2008 7:24 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
